<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <h1>this is a custom Css</h1>

    <div style="kleur: groen;">
        this is custom Css decoration sentence，it's color is kleur: groen
    </div>
</body>
</html>